Combined steam and gas turbine power plant



July 13, 1965 P. H. PACAULT COMBINED STEAM AND GAS TURBINE POWER PLANT Filed Nov. 13, 1961 INVENTOR.

Pierre Henri Pacaulf ATTORNEY pheric pressure.

United States Patent 3,194,015 COMBINED STEAM AND GAS TURBINE HUWER PLANT Pierre Henri Pacault, Ville dAvray, France, assignor to Babcoclc & Wilcox, Limited, LondemEngland, a company of Great Britain Filed Nov. 13, 1961, Ser. No. 151,863 Claims priority, appiication France, Nov. 16, 1960, 844,042 4 Claims. (Cl. oil-39.18)

This invention relates to binary elastic fluid power plants and more particularly to improvements in the construction and operation of supercharged or combined gas and steam turbine power plants.

The use of a gas turbine to supercharge a steam generator is well known in the art. The term supercharged as used herein means a combustion process wherein the pressure of the gases generated in the steam generator is of such a magnitude that useful work may be done by these gases after leaving the steam generator through expansion in a gas turbine to essentially atmos- In this combination, a steam generator is constructed and arranged to deliver superheated steam to a steam turbine, while passing high temperature gases to a gas turbine, with the gas turbine driving a compressor which supplies the air required for maintaining high pressure combustion in the furnace of the steam generator. Experience has shown that one of the major drawbacks of a supercharged power plant of this character is its lack of flexibility in regulation, particularly at low loads, chiefly because of the limitations imposed in respect of the choice of output and pressure supplied by the air compressor.

In accordance with the invention, greatly improved flexibility in regulation of a power plant of the character described is provided by arranging the air compressor so that it is driven by a steam turbine using the first expansion of at least part of the superheated steam supplied by the steam generator. Various means of regulating this turbine permit a variation in the air output of the steam turbine-driven compressor in harmony with the requirements of the steam generator. Provisions are also made for regulating steam and gas temperatures to the steam and gas turbines.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

The single figure is a diagrammatic illustration of a combined condensing steam power plant and a gas turbine power plant constructed and arranged in accordance with my invention.

In the binary elastic fluid power plant illustrated, a compressor 3 discharges air at high pressure through a conduit 4 and branch conduit 5 to the furnace of a supercharged natural circulation steam generator 1 for mixing with fuel supplied to the furnace by way of a conduit 2. The steam generator comprises a steam and water drum 9 constructed and arranged to receive steam and water mixtures from a steam generating section 6 and to supply saturated steam to a superheating section 7, with subsequent reheating of the steam being provided by reheating section 8. Feedwater, after being preheated in feedwater heaters 22, 37, 38 and 39, enters the steam generating section 6 and passes therethrough to the steam-water drum 9 wherein the steam is separated from the water 3,194,615 Patented July 13, 1965 ice and passed through the steam superheating section 7 for superheating to the desired degree.

From the furnace the products of combustion pass over and in contact with the steam generating and heating sections 6, 7 and 8 to a gas outlet 10, then are directed to a gas turbine 11 by way of a conduit 46 and a secondary combustion chamber 12 wherein the temperature and quantity of gases supplied to the gas turbine 11 may be increased by the combustion of a fuel introduced into the chamber 12 by a conduit 13 under control of a valve 141, with the combustion air to the chamber 12 being supplied by the compressor 3 by way of the conduit 4, air control valve 16 and a conduit 15. Another portion of the air delivered by the compressor may by-pass the steam generator 1 by way of a branch conduit 17 leading from the conduit 4 to the conduit 49 and controlled by a valve 18. Control of air flow through the conduit 17 serves to regulate the superheat and reheat steam temperatures since air supply to the furnace of the steam generator is altered by such control. Regulation of the temperature of the gases entering the gas turbine 11 is provided by turbine gas inlet temperature transmitters 14A and 16A which respectively control the operation of the fuel supply valve 14 and the air regulating valve 16. The gases discharged from the secondary combustion chamber 12 go to the gas turbine 11, through which they expand to atmospheric pressure, producing mechanical energy to drive an electric generator 21 directly connected to the shaft of the gas turbine 11. Heat from the gas turbine exhaust is recovered before discharging to a stack 23 by passing the gases through a heat exchanger 22 in direct heat transfer relation with feedwater passing to the steam generator 1.

In accordance with the invention, steam separated in the drum 9 and superheated in the steam superheating section 7 is directed by way of a conduit 41 and a regulating valve 25 to a high pressure steam turbine 26, through which it expands, producing sufficient mechanical energy to drive the compressor 3 which is directly connected to the shaft of the steam turbine 26. Thus the power supplied by the expansion of the superheated steam by the turbine 26 is directly used in the compression of the combustion air of the plant. A starting motor 28 is provided to turn over the compressor 3 and the connected steam turbine 26 until such time as the pressure, temperature and flow conditions of the steam leaving the superheating section 7 are adequate to produce the required driving power by the steam turbine.

' After expansion in the turbine 26, steam is directed through a conduit 43 and regulating valve 29 to the reheating section 8, with a small quantity of the steam being bled to a feedwater heater 39 by way of a valvecontrolled conduit 30.

According to circumstances, the turbine 26 may receive all or a part of the steam fiow from the superheating section 7. In the latter case, the turbine 26 is arranged, as shown by a dotted line in the drawing, in parallel with a second high pressure turbine 26A, the two turbines 26, 26A thus constituting the high pressure stage of the group of steam turbines of the power plant.

The steam reheated in the heating section 8 is discharged through a conduit 44 and a regulating valve 31 to a medium and/or low pressure turbine 32, through which the steam expands with a reduction in pressure to the vacuum of a condenser 36, while developing mechanical power which is transmitted to a directly connected electrical generator 33. When provided, the turbine 26A is directly coupled to the shaft of the turbine 32 and cooperates with the turbine 32 in driving the generator 33.

The condensate resulting from the turbine exhaust steam in the condenser 36 is withdrawn by a condensate 7 tion 6.

pump, not shown, and is progressively heated as itrflows to the steam generating section 6 in heaters 37 and 38' by steam bled from selected pressure stages of the tu-r-t bine 32 through conduits and 34, and in heater)??? by steam bled from the conduit 43 through conduit. 36.

' proportion to increases and decreases At a point between the heaters37 and 33 a part of the feedwater flow is directed through a conduit 45 to the heater 22 for indirect heating bythe exhaust gases of the v turbinel l, thenpa sses through a conduit 46 to-rejoin the main flow of feedwater to the steam gene-rating sectWith a'power plant constructed and arranged as de- "scribed, considerable flexibility in operation is provided,

particularly at low' loads. In this connection the superheat and reheat steam temperatures may be regulated by varying the quantity of air by-passingthe'steam generator by means ofthe valve 18. Varying thequantity of air passing through the conduit 17 will alter the supply of in}; the amount of heat absorbed radiantly by the steam generating section 6,'Wl1ll6 at, the same time varying the quantity of products of" combustion passing. over the t steam generating and heating sections 6, 7 and 3, so that superheat and reheat steam temperatures will be altered.

in steam flow rate to said first ,steamturbine to provide an air flow to said generator at a rate in proportion to the combustion air demands of the'fuel being burned so that the rate of generation of the cheating gases in the generator increases and decreases in proportion to the air compressor output.

3. Ina binary elastic fiuid power plant, a steam genorator including a superheater, fuel firing means for generating heating gases in saidgenerator, a'gas turbine, a secondary combustion chamber connected to receive gases from said steam generator andto discharge gases tosaid gas turbine, means for firing said secondary com- I bustion chamber to regulate the temperature and supply air to the furnace of the steam generator.' Variation of, i the air supply to the 'furnace of the steam generator. Wil1- efiect a'change in the furnace temperature,thereby alter- While in accordancerwith the provisions ofthestatutesv there is illustrated and described herein a specific embodirr, ment' of the invention,'those skilled in-the art will unde-rstand that changes, may be made in the formv of the invention covered by the, claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

What is claimed is:

1. In a binary elastic fluid power plant, a steam generator, fuel firing means for generating heating gases in g said generatorfla gas turbine receiving gases from said steam generator, a heat exchanger connected for flow of gases from said gas'turbine for recovery of somejof the residual heat thereof, a steam turbine receivinglsteam from said steam generator, and an air compressor driven] by said steam turbine and operating independently of said gas turbine and supplying high pressureair for combustion to said fuel firing means, said air compressor having an outputvarying in direct proportion to increases and decreases in steam 'flow rate to said steam turbine to providean airflow to said generator at'a rateiin proportion to the combustion air demands of the fuel being burned so that the rate of generationiof heating gases in the generator increases and decreases in proportion to" the air compressor output. 5

2. In a ibinary elastic fluid power plant, a

' erator, fuel firing means for generating heating gases in said generator,'a gas turbine receiving gases'fromxsaid steam generator, .aheat exchanger connected for flow ing independentlyof said gas turbine and supplying high pressure airtor combustion to said fuel'firing means,

steam gen of gases passing to said gas'turbine, a heat exchanger connected for flow of gases from said gas turbine for recovery of some of the residual heat thereof, a first steam turbine receiving a part of the superheated steam leaving said superheater, a second steam turbine receiving the rest of'the superheated steam leaving said superheater and connectedin parallel flow relation with said first steam turbine, an air compressor driven by said first steanrturbine and[operatingindependently of said gas turbine, means supplying high pressure air for combustion from said compressor in parallel to said fuel firing means of said steam generator and of said secondaryicombustion chamber, andmeans for regulating the temperature of the steam leaving said superheater including a valve-controlled; conduit for passing a part of the steam generator combustion air supply to the gas inlet of the secondary combustion chamber, said air compressor having an output varying in direct proportion to increasesand decreases in steam flow rate to said first steamturbine to provide an air flow to said generator at a rate in proportion to the combustion-air demands of the fuel being burned so that the rate of generation of heating gases in the generator increases and decreases in proportion to the air compressor output. V

4. in a binary elastic fluid power plant, a steam generator, fuel firing means for'generating heating gases in 'said generaton a gas turbine, a secondary combustion chamber connected for supply of gases to' said gas turbine, said gas turbine being connected'tosaid generator via said secondary combustion chamber, fuel firing means 7 for generating heating gases in said secondary combustion ,chamber, -a heat exchanger connected for flow of gases from said'gasturbinefor recovery of some of the residual "heat thereof, a steam turbine receiving steam from said steam" generator, and an air compressor driven by said.

steam turbineand operating independently of said gas turbine and supply high pressure air for combustion to the fuel firing means of said steam generator and of said secondary combustion chamber, said air compressor hav-v ing an output varying iii-direct, proportion to increases and decreases in steam flow rate to'said steam turbine to provide an air How to said generator at a rate in pro-. portion to the combustion air-demands of the fuel being burned in the generator so that the rate of generation of theheating gases in the generator increases and decreases in proportion :to the air compressor output.

References Cited by the Examiner i UNITED STATESfPATENTS 2/41 Holzwarth 60-39.18 2,946,181 7/60 'Zoschak n 60 39.18

OTHERf REF RENCES j The Prospects of MHD Power, Generation, by Steg said air compressor having an output varying in direct V et al., Astronautics V Magazine,

August 0, pages 22-25, P ge'23 relied on." 1

SAMUEL LEVINE, Primary Examiner;

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,194,015 July 13, 196

Pierre Henri Pacault It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 32, for "direct" read indirect Signed and sealed this 12th day of April 1966.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents 

1. IN A BINARY ELASTIC FLUID POWER PLANT, A STEAM GENERATOR, FUEL FIRING MEANS FOR GENERATING HEATING GASES IN SAID GENERATOR, A GAS TURBINE RECEIVING GASES FROM SAID STEAM GENERATOR, A HEAT EXCHANGER CONNECTED FOR FLOW OF GASES FROM SAID GAS TURBINE FOR RECOVERY OF SOME OF THEM RESIDUAL HEAT THEREOF, A STEAM TURBINE RECEIVING STEAM FROM SAID STEAM GENERATOR, AND AN AIR COMPRESSOR DRIVEN BY SAID STEAM TURBINE AND OPERATING INDEPENDENTLY OF SAID GAS TURBINE AND SUPPLYING HIGH PRESSURE AIR FOR COMBUSTION TO SAID FUEL FIRING MEANS, SAID AIR COMPRESSOR HAVING AN OUTPUT VARYING IN DIRECT PROPORTION TO INCREASE AND DECREASES IN STEAM FLOW RATE TO SAID STEAM TURBINE TO PROVIDE AN AIR FLOW TO SAID GENERATOR AT A RATE IN PROPORTION TO THE COMBUSTION AIR DEMANDS OF THE FUEL BEING BURNED SO THAT THE RATE OF GENERATION OF HEATING GASES IN THE GENERATOR INCREASES AND DECREASES IN PROPORTION TO THE AIR COMPRESSOR OUTPUT. 